An ontology  contains a set of entities related amongst themselves by different relations. Ontology entities can be divided in subsets as follows: classes, C, defines the concepts within the ontology; individuals, I, denotes the object instances of these classes; literals, L, represents concrete data values; datatypes, T, defines the types that these values can have; and properties, P, comprises the definitions of possible associations between individuals, called object properties, or between one individual and a literal, called datatype properties. Four specific relations form part of an ontology: specialization or subsumption, ≦; exclusion or disjointness, ⊥; instantiation or membership, ε; and assignment, =.
The Web Ontology Language (OWL), a World Wide Web Recommendation, is a standardized formalism for representing ontologies. In particular, the OWL-DL sublanguage of OWL supports the representation of ontologies with maximum expressiveness without losing computational completeness and decidability, by restricting type separation so that the sets C, P, L, I, and T in the ontology are disjoint. The ASMOV alignment algorithm presented assumes that the ontologies to be aligned are expressed in OWL-DL.
The objective of ontology matching is to automatically derive an alignment between two ontologies, where an alignment consists of a set of correspondences between their elements. Given two ontologies,  and ′, a correspondence between entities e in  and e′ in ′, which we denote as e,e′, signifies that e and e′ are deemed to be equivalent in some semantic sense.
Most work on ontology matching has focused on syntactic approaches, exploiting features including: terminological or lexical similarity between strings representing entities in ontologies; structural similarity at the level of ancestor-descendant and other relationships between entities; and extensional similarity, examining the data instances belonging to each ontology entity. Since entities in ontologies are intended to depict concepts and relationships with specific meaning, it is clear that correspondences found through ontology matching must abide by and be coherent with the formal semantics of the ontologies themselves.
Accordingly, it is desirable to derive systems and methods that fulfill these characteristics and that overcome existing deficiencies in the state of the art.